U.S. Pat. No. 4,035,214 to Shuppert, et al. describes a printing system in which a release blanket is coated with a transparent film. A multi-color image is printed onto the release film and film, together with the images is transferred, image side down, onto a can. The release thus acts as a protective coating for the image. A film of adhesive is applied either to the image or to the can so that the film will transfer from the release blanket. The images are preferably printed by flexographic, letter press or other systems utilizing raised ink applicators.
U.S. Pat. No. 4,949,103 describes a direct electrostatic printing apparatus in which charged toner is applied by a print-head structure to a film coated with an adhesive to produce a “reverse reading image.” The film with the image thereon are adhered to a final surface, with the image facing the final surface by the adhesive. The printed images may be alphanumeric text (for use in address labels) or a picture (for use in an identification badge).
It is well known in the art to print various types of images on paper or some other surface and then to laminate the printed image using either a single sheet of plastic material attached to the printed surface or by laminating a printed sheet between two sheets of plastic. In general, the plastic sheets are coated on one side with an adhesive material which adheres to the image. In some prior art systems the adhesive is not sticky at room temperature and the lamination process is carried out which subjecting the plastic sheet and the printed substrate to heat and pressure.
However, when thick plastic material is used, the image appears to be behind the front surface, which is not esthetically pleasing. On the other hand, when utilizing thinner plastic sheets, the structure or substructure of the printed sheet transfers to the front surface, reducing the quality of the resulting product.
These problems form a limitation on the use of such lamination in producing digital photographic prints (referred to herein as “digital photo-finishing”), i.e., the limitations on the surface finish available. In particular, laminated images, even when produced with very smooth plastic film, tend to have, on them, a pattern or other variations, unless they are thick. These variations on the surface may be due to the surface of the film following the surface texture of the paper to which it is bonded, or other causes.
WO 99/19733 and PCT applications PCT/IL00/0084, entitled “Printing on Plastic” and PCT/IL99/00510, entitled “Substrate Coating for Improved Toner Transfer and Adhesion”, the disclosures of all of which are incorporated herein by reference, describe coating of plastic sheets with layer(s) which adhere to the sheets and to which liquid toners can be transferred and bonded. In general, these coatings comprise thermoplastic material.
It is known in the art to coat paper or other materials with thin layers of plastic. One method of coating, called casting, comprises extruding a thin layer of the plastic of the paper on the paper and then passing the coated paper through a pair of rollers, while the plastic is still hot. The plastic replicates the finish of the roller that touches it. One use for such coated paper is as a substrate for various printing processes.